Process and device for continuous tonic monitoring of aqueous solutions

Abstract

An electrolytic process and apparatus are disclosed for continuously producing the cation conductivity, anion conductivity, and temperature data required for continuous monitoring of the pH of high-purity aqueous solution flows. The cation exchange material and the anion exchange material used for conditioning water samples for conductivity measurements are continuously regenerated by applying a DC electric voltage between an anode and a cathode either across the cation exchange material, whereby hydrogen ions generated at the anode move through the cation exchange material displacing cations previously absorbed and these displaced cations under the influence of the electric field migrate to the cathode, or across the anion exchange material, whereby hydroxyl ions generated at the cathode regenerate the anion exchange material. The temperature-corrected cation conductivity and the temperature-corrected anion conductivity are then used together with measurement of the specific conductivity of the sample to calculate the pH of the sample.

What is claimed is:  
     
         1 . Apparatus for determining the ionic purity of an aqueous sample, said apparatus comprising: 
 a conductivity meter for measuring the conductivity and temperature of a sample;    a cation exchange element for exchanging cations present in a cation portion of said sample for hydrogen ions while said cation portion is passing in contact with said cation exchange element;    a conductivity meter for measuring the conductivity and temperature of said cation portion after contact with said cation exchange element;    a cation exchange element regeneration system for continuously regenerating said cation exchange element by displacing cations removed from said cation portion with new hydrogen ions generated by electrolysis of water;    an anion exchange clement for exchanging anions present in an anion portion of said sample for hydroxyl ions while said anion portion is passing in contact with said anion exchange element;    a conductivity meter for measuring the conductivity and temperature of said anion portion after contact with said anion exchange element; and,    an anion exchange element regeneration system for continuously regenerating said anion exchange element by displacing anions removed from said anion portion with new hydroxyl ions generated by electrolysis of water.    
     
     
         2 . Apparatus according to  claim 1  wherein said cation exchange element regeneration system comprises: 
 an anode compartment including an anode, an anode compartment inlet end, and an anode compartment outlet end;  
 a cathode compartment including a cathode, a cathode compartment inlet end, and a cathode compartment outlet end;  
 a direct current power source;  
 at least a cation exchange membrane disposed to form a cation membrane compartment, said cation membrane compartment having a cation membrane compartment inlet and a cation membrane compartment outlet; and,  
 a cation exchange material disposed in said cation membrane compartment.  
 
     
     
         3 . Apparatus according to  claim 1  wherein said anion exchange element regeneration system comprises: 
 an anode compartment including an anode, an anode compartment inlet end, and an anode compartment outlet end;  
 a cathode compartment including a cathode, a cathode compartment inlet end, and a cathode compartment outlet end;  
 a direct current power source;  
 at least an anion exchange membrane disposed to form an anion membrane compartment, said anion membrane compartment having an anion membrane compartment inlet and an anion membrane compartment outlet; and,  
 an anion exchange material disposed in said anion membrane compartment.  
 
     
     
         4 . Apparatus according to  claim 1  wherein said cation exchange element regeneration system further comprises: 
 two electrically insulating planar elements, a first of said planar elements comprising a fluid inlet and a fluid outlet pair and a sample stream channel disposed therebetween along one face thereof; a second of said planar elements comprising two fluid inlet and fluid outlet pairs, each having an electrode channel therebetween, along one face thereof;  
 an anode contained in one of said electrode channels and a cathode contained in the other of said electrode channels; and,  
 a cation exchange membrane disposed between said two planar elements, said membrane being in contact with said anode and said cathode along one surface of said membrane and being in contact with said sample stream channel along the opposite surface.  
 
     
     
         5 . Apparatus according to  claim 1  wherein said anion exchange element regeneration system further comprises: 
 two electrically insulating planar elements, a first of said planar elements comprising a fluid inlet and a fluid outlet pair and a sample stream channel disposed therebetween along one face thereof; a second of said planar elements comprising two fluid inlet and fluid outlet pairs, each having an electrode channel therebetween, along one face thereof;  
 an anode contained in one of said electrode channels and a cathode contained in the other of said electrode channels; and,  
 an anion exchange membrane disposed between said two planar elements, said membrane being in contact with said anode and said cathode along one surface of said membrane and being in contact with said sample stream channel along the opposite surface.  
 
     
     
         6 . Apparatus according to  claim 2  wherein said anode and said cathode compartments are filled with a cation exchange material.  
     
     
         7 . Apparatus according to  claim 3  wherein said anode and said cathode compartments are filled with an anion exchange material.  
     
     
         8 . Apparatus according to  claim 2  wherein said anode and said cathode are in contact with a cation exchange membrane.  
     
     
         9 . Apparatus according to  claim 3  wherein said anode and said cathode are in contact with an anion exchange membrane.  
     
     
         10 . A system for measuring the ionic purity of a flowing aqueous sample, said system comprising: 
 a means of measuring the conductivity and temperature of a flowing sample stream;    a means of splitting said flowing sample stream into two substantially equal split sample streams;    a means for continuously exchanging cations for hydrogen ions in one of said split sample streams, and for continuously exchanging anions for hydroxyl ions in the other of said split sample streams;    a means of measuring both the conductivity and temperature of each of said split sample streams following said continuous ion exchange;    a means of calculating the pH of the sample stream using the temperature and conductivity of the original sample stream and of said two split ion-exchanged sample streams.    
     
     
         11 . A method for determining the ionic purity of an aqueous sample, said method comprising the steps of: 
 measuring the conductivity and temperature of said sample;    continuously exchanging cations in a cation portion of said sample for hydrogen ions by contact with a cation exchange element;    continuously regenerating said cation exchange element with new hydrogen ions;    measuring the conductivity and temperature of said cation portion of said sample exiting from said contact with a cation exchange element;    continuously exchanging anions in an anion portion of said sample for hydroxyl ions by contact with an anion exchange element;    continuously regenerating said anion exchange element with new hydroxyl ions;    measuring the conductivity and temperature of said anion portion of said sample exiting from said contact with an anion exchange element; and,    calculating the ionic purity of the sample based on said conductivity and temperature measurements.    
     
     
         12 . A method according to  claim 11  wherein the exchanging of cations for hydrogen ions and the continuous regeneration of said cation exchange element is performed using: 
 an anode compartment means with an anode, an inlet end, and an outlet end;  
 a cathode compartment means with a cathode, an inlet end, and an outlet end;  
 a direct current power source;  
 two cation exchange membranes disposed to form a compartment between them, said compartment having an inlet means and an outlet means; and,  
 a cation exchange material disposed in said compartment between said membranes.  
 
     
     
         13 . A method according to  claim 11  wherein the exchanging of anions for hydroxyl ions and the continuous regeneration of said anion exchange element is performed using: 
 an anode compartment means with an anode, an inlet end, and an outlet end;  
 a cathode compartment means with a cathode, an inlet end, and an outlet end;  
 a direct current power source;  
 two anion exchange membranes disposed to form a compartment between them, said compartment having an inlet means and an outlet means; and,  
 an anion exchange material disposed in said compartment between said membranes.  
 
     
     
         14 . A method according to  claim 11  wherein the exchanging of cations for hydrogen ions and the continuous regeneration of said cation exchange element is performed using: 
 two electrically insulating plates; with one of said plates having an inlet, an outlet and a channel for the sample stream disposed between said inlet and out on one side of said plate; second said plate having an inlet, an outlet, and a channel between said inlet and outlet containing an anode, and having an inlet and outlet on the same side of said plate and a channel between said inlet and outlet containing a cathode; and,  
 a cation exchange membrane disposed between two said plates, having contact with said anode and said cathode on one side and contact with said sample stream channel on the opposite side.  
 
     
     
         15 . A method according to  claim 11  wherein the exchanging of anions for hydroxyl ions and the continuous regeneration of said anion exchange element is performed using: 
 two electrically insulating plates; with one of said plates having an inlet, an outlet and a channel for the sample stream disposed between said inlet and out on one side of said plate; second said plate having an inlet, an outlet, and a channel between said inlet and outlet containing an anode, and having an inlet and outlet on the same side of said plate and a channel between said inlet and outlet containing a cathode; and,  
 an anion exchange membrane disposed between two said plates, having contact with said anode and said cathode on one side and contact with said sample stream channel on the opposite side.  
 
     
     
         16 . A method according to  claim 12  wherein said anode and said cathode compartments are filled with a cation exchange material.  
     
     
         17 . A method according to  claim 13  wherein said anode and said cathode compartments are filled with an anion exchange material.  
     
     
         18 . A method according to  claim 12  wherein said anode and said cathode are in contact with a cation exchange membrane.  
     
     
         19 . A method according to  claim 13  wherein said anode and said cathode are in contact with an anion exchange membrane.  
     
     
         20 . A method for measuring the ionic purity of an aqueous sample, said method comprising the steps of: 
 measuring the conductivity and temperature of a sample stream;    splitting said sample stream into two substantially equal split sample streams;    continuously exchanging cations for hydrogen ions in one of said split sample streams and continuously exchanging anions for hydroxyl ions in the other of said split sample streams;    measuring both the conductivity and temperature of each of said split sample streams following said continuous ion exchange; and,    calculating the pH of the sample stream using the temperature and conductivity of the original sample stream and of said two split ion-exchanged sample streams.    
     
     
         21 . Apparatus for determining the cation conductivity of an aqueous sample, said apparatus comprising: 
 a cation exchange element for exchanging cations present in said sample for hydrogen ions while said sample is passing in contact with said cation exchange element;    a conductivity meter for measuring the conductivity and temperature of said sample after contact with said cation exchange element; and,    a cation exchange element regeneration system for continuously regenerating said cation exchange element by displacing cations removed from said cation portion with new hydrogen ions generated by electrolysis of water.    
     
     
         22 . Apparatus according to  claim 21  wherein said cation exchange element regeneration system comprises: 
 an anode compartment including an anode, an anode compartment inlet end, and an anode compartment outlet end;  
 a cathode compartment including a cathode, a cathode compartment inlet end, and a cathode compartment outlet end;  
 a direct current power source;  
 at least a cation exchange membrane disposed to form a cation membrane compartment, said cation membrane compartment having a cation membrane compartment inlet and a cation membrane compartment outlet; and,  
 a cation exchange material disposed in said cation membrane compartment.  
 
     
     
         23 . Apparatus according to  claim 22  wherein said anode and said cathode compartments are filled with a cation exchange material.  
     
     
         24 . Apparatus according to  claim 22  wherein said anode and said cathode are in contact with a cation exchange membrane.  
     
     
         25 . Apparatus according to  claim 21  wherein said cation exchange element regeneration system further comprises: 
 two electrically insulating planar elements, a first of said planar elements comprising a fluid inlet and a fluid outlet pair and a sample stream channel disposed therebetween along one face thereof; a second of said planar elements comprising two fluid inlet and fluid outlet pairs, each having an electrode channel therebetween, along one face thereof;  
 an anode contained in one of said electrode channels and a cathode contained in the other of said electrode channels; and,  
 a cation exchange membrane disposed between said two planar elements, said membrane being in contact with said anode and said cathode along one surface of said membrane and being in contact with said sample stream channel along the opposite surface.  
 
     
     
         26 . Apparatus for determining the anion conductivity of an aqueous sample, said apparatus comprising: 
 an anion exchange element for exchanging anions present in said sample for hydroxyl ions while said sample is passing in contact with said anion exchange element;    a conductivity meter for measuring the conductivity and temperature of said sample after contact with said anion exchange element; and,    an anion exchange element regeneration system for continuously regenerating said anion exchange element by displacing anions removed from said anion portion with new hydroxyl ions generated by electrolysis of water.    
     
     
         27 . Apparatus according to  claim 26  wherein said anion exchange element regeneration system comprises: 
 an anode compartment including an anode, an anode compartment inlet end, and an anode compartment outlet end;  
 a cathode compartment including a cathode, a cathode compartment inlet end, and a cathode compartment outlet end;  
 a direct current power source;  
 at least an anion exchange membrane disposed to form an anion membrane compartment, said anion membrane compartment having an anion membrane compartment inlet and an anion membrane compartment outlet; and,  
 an anion exchange material disposed in said anion membrane compartment.  
 
     
     
         28 . Apparatus according to  claim 27  wherein said anode and said cathode compartments are filled with an anion exchange material.  
     
     
         29 . Apparatus according to  claim 27  wherein said anode and said cathode are in contact with an anion exchange membrane.  
     
     
         30 . Apparatus according to  claim 26  wherein said anion exchange element regeneration system further comprises: 
 two electrically insulating planar elements, a first of said planar elements comprising a fluid inlet and a fluid outlet pair and a sample stream channel disposed therebetween along one face thereof; a second of said planar elements comprising two fluid inlet and fluid outlet pairs, each having an electrode channel therebetween, along one face thereof;  
 an anode contained in one of said electrode channels and a cathode contained in the other of said electrode channels; and,  
 an anion exchange membrane disposed between said two planar elements, said membrane being in contact with said anode and said cathode along one surface of said membrane and being in contact with said sample stream channel along the opposite surface.  
 
     
     
         31 . A method for determining the cation conductivity of an aqueous sample, said method comprising the steps of: 
 continuously exchanging cations in said sample for hydrogen ions by contact with a cation exchange element;    continuously regenerating said cation exchange element with new hydrogen ions; and,    measuring the conductivity and temperature of said sample exiting from said contact with a cation exchange element.    
     
     
         32 . A method according to  claim 31  wherein the exchanging of cations for hydrogen ions and the continuous regeneration of said cation exchange element is performed using: 
 an anode compartment means with an anode, an inlet end, and an outlet end;  
 a cathode compartment means with a cathode, an inlet end, and an outlet end;  
 a direct current power source;  
 two cation exchange membranes disposed to form a compartment between them, said compartment having an inlet means and an outlet means; and,  
 a cation exchange material disposed in said compartment between said membranes.  
 
     
     
         33 . A method according to  claim 31  wherein the exchanging of cations for hydrogen ions and the continuous regeneration of said cation exchange element is performed using: 
 two electrically insulating plates; with one of said plates having an inlet, an outlet and a channel for the sample stream disposed between said inlet and out on one side of said plate; second said plate having an inlet, an outlet, and a channel between said inlet and outlet containing an anode, and having an inlet and outlet on the same side of said plate and a channel between said inlet and outlet containing a cathode; and,  
 a cation exchange membrane disposed between two said plates, having contact with said anode and said cathode on one side and contact with said sample stream channel on the opposite side.  
 
     
     
         34 . A method for determining the anion conductivity of an aqueous sample, said method comprising the steps of: 
 continuously exchanging anions in said sample for hydroxyl ions by contact with an anion exchange element;    continuously regenerating said anion exchange element with new hydroxyl ions; and,    measuring the conductivity and temperature of said anion portion of said sample exiting from said contact with an anion exchange element.    
     
     
         35 . A method according to  claim 34  wherein the exchanging of anions for hydroxyl ions and the continuous regeneration of said anion exchange element is performed using: 
 an anode compartment means with an anode, an inlet end, and an outlet end;  
 a cathode compartment means with a cathode, an inlet end, and an outlet end;  
 a direct current power source;  
 two anion exchange membranes disposed to form a compartment between them, said compartment having an inlet means and an outlet means; and,  
 an anion exchange material disposed in said compartment between said membranes.  
 
     
     
         36 . A method according to  claim 34  wherein the exchanging of anions for hydroxyl ions and the continuous regeneration of said anion exchange element is performed using: 
 two electrically insulating plates; with one of said plates having an inlet, an outlet and a channel for the sample stream disposed between said inlet and out on one side of said plate; second said plate having an inlet, an outlet, and a channel between said inlet and outlet containing an anode, and having an inlet and outlet on the same side of said plate and a channel between said inlet and outlet containing a cathode; and,  
 an anion exchange membrane disposed between two said plates, having contact with said anode and said cathode on one side and contact with said sample stream channel on the opposite side.